Communications device and method

ABSTRACT

A communications device includes a transmitter configured to transmit signals to one or more other communications devices via a wireless access interface, the one or more communications devices configured to perform device-to-device communications. A receiver is configured to receive signals from the one of the other communications devices via the wireless access interface, and a controller controls the transmitter and receiver to transmit or to receive the signals via the wireless access interface to transmit or to receive data represented by the signals. The wireless access interface provides a scheduling region including plural predetermined sections of communications resources, and plural sections of shared communications resources. Transmission of a scheduling assignment message in a section of the scheduling region informs other devices of a group that a communications device will transmit signals representing data in a corresponding section of the shared communications channel.

TECHNICAL FIELD OF THE DISCLOSURE

The present disclosure relates to communications devices and methods forcommunicating data using communications devices, and in particular tocommunications devices which are configured to perform device-to-devicecommunications.

BACKGROUND OF THE DISCLOSURE

Mobile telecommunication systems, such as those based on the 3GPPdefined UMTS and Long Term Evolution (LTE) architecture, are able tosupport more sophisticated services than simple voice and messagingservices offered by previous generations of mobile telecommunicationsystems. For example, with the improved radio interface and enhanceddata rates provided by LTE systems, a user is able to enjoy high datarate applications such as video streaming and video conferencing onmobile communications devices that would previously only have beenavailable via a fixed line data connection.

The demand to deploy fourth generation networks is therefore strong andthe coverage area of these networks, i.e. geographic locations whereaccess to the networks is possible, is expected to increase rapidly.However, although the coverage and capacity of fourth generationnetworks is expected to significantly exceed those of previousgenerations of communications networks, there are still limitations onnetwork capacity and the geographical areas that can be served by suchnetworks. These limitations may, for example, be particularly relevantin situations in which networks are experiencing high load and high-datarate communications between communications devices, or whencommunications between communications devices are required but thecommunications devices may not be within the coverage area of a network.In order to address these limitations, in LTE release-12 the ability forLTE communications devices to perform device-to-device (D2D)communications will be introduced.

D2D communications allow communications devices that are in closeproximity to directly communicate with each other, both when within andwhen outside of a coverage area or when the network fails. This D2Dcommunications ability can allow user data to be more efficientlycommunicated between communications devices by obviating the need foruser data to be relayed by a network entity such as a base station, andalso allows communications devices that are in close proximity tocommunicate with one another although they may not be within thecoverage area of a network. The ability for communications devices tooperate both inside and outside of coverage areas makes LTE systems thatincorporate D2D capabilities well suited to applications such as publicsafety communications, for example. Public safety communications requirea high degree of robustness whereby devices can continue to communicatewith one another in congested networks and when outside a coverage area.

Fourth generation networks have therefore been proposed as a costeffective solution to public safety communications compared to dedicatedsystems such as TETRA which are currently used throughout the world.However, the potential coexistence of conventional LTE communicationsand D2D communications within a single coverage area or network mayincrease the complexity of coordinating communications and resourceallocation within an LTE network, and may also lead to potentialcompatibility issues between conventional and D2D capable LTEcommunications devices.

SUMMARY OF THE DISCLOSURE

According to a first example embodiment of the present technique thereis provided a communications device comprising a transmitter configuredto transmit signals to one or more other communications devices via awireless access interface, the one or more communications devices beingarranged to perform device-to-device (D2D) communications. A receiver isconfigured to receive signals from the one of the other communicationsdevices via the wireless access interface, and a controller controls thetransmitter and the receiver to transmit or to receive the signals viathe wireless access interface to transmit or to receive data representedby the signals. The wireless access interface provides a schedulingregion comprising a plurality of predetermined sections ofcommunications resources, and a plurality of predetermined sections ofshared communications resources. Each of the plurality of predeterminedsections of the scheduling region corresponds to at least one of theplurality of sections of the shared communications resources, so thattransmitting in one of the plurality of the sections of the schedulingregion reserves the corresponding section or sections of the sharedcommunications resources for transmitting the signals representing thedata.

Example embodiments of the present technique can provide a schedulingregion or channel within a wireless access interface in whichcommunications devices can transmit scheduling assignment messages inorder to reserve corresponding sections of communications resources of ashared communications channel. Accordingly, a communications devicewhich wishes to transmit data to other communications devices in a groupmay transmit a scheduling assignment message in one or more of theplurality of predetermined sections of the scheduling region. Thetransmission of the scheduling assignment message in a section of thescheduling region informs the other devices of the group that acommunications device will transmit signals representing data in acorresponding section of the shared communications channel. Otherdevices in the group which are not transmitting therefore monitor thescheduling region and if they detect a scheduling assignment messagetransmitted in one or more sections of the schedule assignment regionthen the devices attempt to detect and decode signals transmitted in acorresponding section of the shared communications resources channel.Accordingly a group of communications device can performdevice-to-device (D2D) communications without the requirement for acentral coordinating entity which can therefore improve efficiency withwhich communications resources are used.

In some examples the wireless access interface is divided into aplurality of time divided units. The schedule assignment region isprovided in one of the time divided units and at least one other of thetime divided units provides the shared communications resources. In someexamples, the schedule assignment region is provided periodically in thetime divided units separated by one or more other time divided unitswhich provide the shared communications resources. Accordingly a powersaving advantage can be provided to communications devices of the groupbecause they only have to power up their receiver to receive thescheduling region periodically, the period corresponding to the relativeratio of the time unit in which the scheduling region is provided withrespect to the time unit or units in which the shared communicationsresources are provided.

Various further aspects and features of the present disclosure aredefined in the appended claims and include a communications device, amethod of communicating using a communications device.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments of the present disclosure will now be described by way ofexample only with reference to the accompanying drawings wherein likeparts are provided with corresponding reference numerals and in which:

FIG. 1 provides a schematic diagram of a mobile communications system;

FIG. 2 provides a schematic diagram of the structure of a downlink of awireless access interface of a mobile communications system;

FIG. 3 provides a schematic diagram of an uplink of a wireless accessinterface of a mobile communications system;

FIG. 4 provides a schematic diagram of a mobile communications system inwhich communications devices can perform device-to-devicecommunications;

FIGS. 5a to 5d provides schematics diagrams of example device-to-devicecommunications scenarios;

FIG. 6 provides a schematic block diagram illustrating an arrangement inwhich a plurality of communications devices form a group which performdevice-to-device communications;

FIG. 7 is a schematic representation of a wireless access interfacecomprising a scheduling region and regions shared communicationsresources and illustrating an operation in accordance with the presenttechnique for supporting device-to-device communications;

FIG. 8 is a schematic block diagram illustrating another arrangement ofa wireless access interface in accordance with the present technique,for supporting device to device communications;

FIG. 9 is a schematic block diagram of a further illustration of awireless access interface for supporting device to device communicationsin accordance with the present technique; and

FIGS. 10a to 10e provide example block diagrams illustrating furtherpossible arrangements of wireless access interfaces in accordance withthe present technique for supporting device-to-device communications.

DESCRIPTION OF EXAMPLE EMBODIMENTS Conventional Communications System

FIG. 1 provides a schematic diagram of a conventional mobiletelecommunications system 100, where the system includes mobilecommunications devices 101, infrastructure equipment 102 and a corenetwork 103. The infrastructure equipment may also be referred to as abase station, network element, enhanced Node B (eNodeB) or acoordinating entity for example, and provides a wireless accessinterface to the one or more communications devices within a coveragearea or cell. The one or more mobile communications devices maycommunicate data via the transmission and reception of signalsrepresenting data using the wireless access interface. The networkentity 102 is communicatively linked to the core network 103 where thecore network may be connected to one or more other communicationssystems or networks which have a similar structure to that formed fromcommunications devices 101 and infrastructure equipment 102. The corenetwork may also provide functionality including authentication,mobility management, charging and so on for the communications devicesserved by the network entity. The mobile communications devices of FIG.1 may also be referred to as communications terminals, user equipment(UE), terminal devices and so forth, and are configured to communicatewith one or more other communications devices served by the same or adifferent coverage area via the network entity. These communications maybe performed by transmitting and receiving signals representing datausing the wireless access interface over the two way communicationslinks represented by lines 104 to 109, where 104, 106 and 108 representdownlink communications from the network entity to the communicationsdevices and 105, 107 and 109 represent the uplink communications fromthe communications devices to the network entity. The communicationssystem 100 may operate in accordance with any known protocol, forinstance in some examples the system 100 may operate in accordance withthe 3GPP Long Term Evolution (LTE) standard where the network entity andcommunications devices are commonly referred to as eNodeB and UEs,respectively.

FIG. 2 provides a simplified schematic diagram of the structure of adownlink of a wireless access interface that may be provided by or inassociation with the eNodeB of FIG. 1 when the communications system isoperating in accordance with the LTE standard. In LTE systems thewireless access interface of the downlink from an eNodeB to a UE isbased upon an orthogonal frequency division multiplexing (OFDM) accessradio interface. In an OFDM interface the resources of the availablebandwidth are divided in frequency into a plurality of orthogonalsubcarriers and data is transmitted in parallel on a plurality oforthogonal subcarriers, where bandwidths between 1.25 MHZ and 20 MHzbandwidth may be divided into 128 to 2048 orthogonal subcarriers forexample. Each subcarrier bandwidth may take any value but in LTE it isfixed at 15 KHz. As shown in FIG. 2, the resources of the wirelessaccess interface are also temporally divided into frames where a frame200 lasts 10 ms and is subdivided into 10 subframes 201 each with aduration of 1 ms.

Each subframe is formed from 14 OFDM symbols and is divided into twoslots each of which comprise six or seven OFDM symbols depending onwhether a normal or extended cyclic prefix is being utilised betweenOFDM symbols for the reduction of intersymbol interference. Theresources within a slot may be divided into resources blocks 203 eachcomprising 12 subcarriers for the duration of one slot and the resourcesblocks further divided into resource elements 204 which span onesubcarrier for one OFDM symbol, where each rectangle 204 represents aresource element.

In the simplified structure of the downlink of an LTE wireless accessinterface of FIG. 2, each subframe 201 comprises a control region 205for the transmission of control data, a data region 206 for thetransmission of user data , reference signals 207 and synchronisationsignals which are interspersed in the control and data regions inaccordance with a predetermined pattern. The control region 204 maycontain a number of physical channels for the transmission of controldata, such as a physical downlink control channel (PDCCH), a physicalcontrol format indicator channel (PCFICH) and a physical HARQ indicatorchannel (PHICH). The data region may contain a number of physicalchannel for the transmission of data, such as a physical downlink sharedchannel (PDSCH) and a physical broadcast channels (PBCH). Furtherinformation on the structure and functioning of the physical channels ofLTE systems can be found in [11].

Resources within the PDSCH may be allocated by an eNodeB to UEs beingserved by the eNodeB. For example, a number of resource blocks of thePDSCH may be allocated to a UE in order that it may receive data that ithas previously requested or data which is being pushed to it by theeNodeB, such as radio resource control (RRC) signalling. In FIG. 2, UE1has been allocated resources 208 of the data region 206, UE2 resources209 and UE resources 210. UEs in a an LTE system may be allocated afraction of the available resources of the PDSCH and therefore UEs arerequired to be informed of the location of their allocated resourceswithin the PDCSH so that only relevant data within the PDSCH is detectedand estimated. In order to inform the UEs of the location of theirallocated communications resources, resource control informationspecifying downlink resource allocations is conveyed across the PDCCH ina form termed downlink control information (DCI), where resourceallocations for a PDSCH are communicated in a preceding PDCCH instancein the same subframe. During a resource allocation procedure, UEs thusmonitor the PDCCH for DCI addressed to them and once such a DCI isdetected, receive the DCI and detect and estimate the data from therelevant part of the PDSCH.

FIG. 3 provides a simplified schematic diagram of the structure of anuplink of an LTE wireless access interface that may be provided by or inassociation with the eNodeB of FIG. 1. In LTE networks the uplinkwireless access interface is based upon a single carrier frequencydivision multiplexing FDM (SC-FDM) interface and downlink and uplinkwireless access interfaces may be provided by frequency divisionduplexing (FDD) or time division duplexing (TDD), where in TDDimplementations subframes switch between uplink and downlink subframesin accordance with predefined patterns. However, regardless of the formof duplexing used, a common uplink frame structure is utilised. Thesimplified structure of FIG. 3 illustrates such an uplink frame in anFDD implementation. A frame 300 is divided in to 10 subframes 301 of 1ms duration where each subframe 301 comprises two slots 302 of 0.5 msduration. Each slot is then formed from seven OFDM symbols 303 where acyclic prefix 304 is inserted between each symbol in a manner equivalentto that in downlink subframes. In FIG. 3 a normal cyclic prefix is usedand therefore there are seven OFDM symbols within a subframe, however,if an extended cyclic prefix were to be used, each slot would containonly six OFDM symbols. The resources of the uplink subframes are alsodivided into resource blocks and resource elements in a similar mannerto downlink subframes.

Each uplink subframe may include a plurality of different channels, forexample a physical uplink shared channel (PUSCH) 305, a physical uplinkcontrol channel (PUCCH) 306, and a physical random access channel(PRACH). The physical Uplink Control Channel (PUCCH) may carry controlinformation such as ACK/NACK to the eNodeB for downlink transmissions,scheduling request indicators (SRI) for UEs wishing to be scheduleduplink resources, and feedback of downlink channel state information(CSI) for example. The PUSCH may carry UE uplink data or some uplinkcontrol data. Resources of the PUSCH are granted via PDCCH, such a grantbeing typically triggered by communicating to the network the amount ofdata ready to be transmitted in a buffer at the UE. The PRACH may bescheduled in any of the resources of an uplink frame in accordance witha one of a plurality of PRACH patterns that may be signalled to UE indownlink signalling such as system information blocks. As well asphysical uplink channels, uplink subframes may also include referencesignals. For example, demodulation reference signals (DMRS) 307 andsounding reference signals (SRS) 308 may be present in an uplinksubframe where the DMRS occupy the fourth symbol of a slot in whichPUSCH is transmitted and are used for decoding of PUCCH and PUSCH data,and where SRS are used for uplink channel estimation at the eNodeB.Further information on the structure and functioning of the physicalchannels of LTE systems can be found in W.

In an analogous manner to the resources of the PDSCH, resources of thePUSCH are required to be scheduled or granted by the serving eNodeB andthus if data is to be transmitted by a UE, resources of the PUSCH arerequired to be granted to the UE by the eNode B. At a UE, PUSCH resourceallocation is achieved by the transmission of a scheduling request or abuffer status report to its serving eNodeB. The scheduling request maybe made, when there is insufficient uplink resource for the UE to send abuffer status report, via the transmission of Uplink Control Information(UCI) on the PUCCH when there is no existing PUSCH allocation for theUE, or by transmission directly on the PUSCH when there is an existingPUSCH allocation for the UE. In response to a scheduling request, theeNodeB is configured to allocate a portion of the PUSCH resource to therequesting UE sufficient for transferring a buffer status report andthen inform the UE of the buffer status report resource allocation via aDCI in the PDCCH. Once or if the UE has PUSCH resource adequate to senda buffer status report, the buffer status report is sent to the eNodeBand gives the eNodeB information regarding the amount of data in anuplink buffer or buffers at the UE. After receiving the buffer statusreport, the eNodeB can allocate a portion of the PUSCH resources to thesending UE in order to transmit some of its buffered uplink data andthen inform the UE of the resource allocation via a DCI in the PDCCH.For example, presuming a UE has a connection with the eNodeB, the UEwill first transmit a PUSCH resource request in the PUCCH in the form ofa UCI. The UE will then monitor the PDCCH for an appropriate DCI,extract the details of the PUSCH resource allocation, and transmituplink data , at first comprising a buffer status report, and/or latercomprising a portion of the buffered data, in the allocated resources.

Although similar in structure to downlink subframes, uplink subframeshave a different control structure to downlink subframes, in particularthe upper 309 and lower 310 subcarriers/frequencies/resource blocks ofan uplink subframe are reserved for control signaling rather than theinitial symbols of a downlink subframe. Furthermore, although theresource allocation procedure for the downlink and uplink are relativelysimilar, the actual structure of the resources that may be allocated mayvary due to the different characteristics of the OFDM and SC-FDMinterfaces that are used in the downlink and uplink respectively. InOFDM each subcarrier is individually modulated and therefore it is notnecessary that frequency/subcarrier allocation are contiguous however,in SC-FDM subcarriers are modulation in combination and therefore ifefficient use of the available resources are to be made contiguousfrequency allocations for each UE are preferable.

As a result of the above described wireless interface structure andoperation, one or more UEs may communicate data to one another via acoordinating eNodeB, thus forming a conventional cellulartelecommunications system. Although cellular communications system suchas those based on the previously released LTE standards have beencommercially successful, a number of disadvantages are associated withsuch centralised systems. For example, if two UEs which are in closeproximity wish to communicate with each other, uplink and downlinkresources sufficient to convey the data are required. Consequently, twoportions of the system's resources are being used to convey a singleportion of data. A second disadvantage is that an eNodeB is required ifUEs, even when in close proximity, wish to communicate with one another.These limitations may be problematic when the system is experiencinghigh load or eNodeB coverage is not available, for instance in remoteareas or when eNodeBs are not functioning correctly. Overcoming theselimitations may increase both the capacity and efficiency of LTEnetworks but also lead to the creations of new revenue possibilities forLTE network operators.

Device-to-Device Communications

D2D communications offer the possibility to address the aforementionedproblems of network capacity and the requirement of network coverage forcommunications between LTE devices. For example, if user data can becommunicated directly between UEs only one set of resources is requiredto communicate the data rather than both uplink and downlink resources.Furthermore, if UEs are capable of communicating directly, UEs withinrange of each other may communicate even when outside of a coverage areaprovided an eNodeB. As a result of these potential benefits, theintroduction of D2D capabilities into LTE systems has been proposed.

FIG. 4 provides a schematic diagram of a mobile communications system400 that is substantially similar to that described with reference toFIG. 1 but where the UEs 401 402 403 are also operable to perform directdevice-to-device (D2D) communications with one another. D2Dcommunications comprise UEs directly communicating data between oneanother without user and or control data being communicated via adedicated coordinating entity such as an eNodeB. For example, in FIG. 4communications between the UEs 401 402 403 415 and the eNodeB 404 are inaccordance with the existing LTE standard, but as well as communicatingvia the uplink and downlinks 405 to 410, when the UEs 401 to 403 arewithin range of each other they may also communicate directly with oneanother via the D2D communication links 411 to 414. In FIG. 4 D2Dcommunications links are indicated by dashed lines and are shown toexist between 401 and 402, and 402 and 403 but not between 401 and 403because these UEs are not sufficiently close together to directlytransmit and receive signals to and from one another. D2D communicationslinks are also shown not to exist between 415 and other UEs because UE415 is not capable of D2D communications. A situation such as thatillustrated in FIG. 4 may exist in an LTE network where UE 415 is adevice not compliant with the specifications for D2D operation.

In order to establish a D2D communications link, such a one-way D2Dcommunications link 414 from the UE 402 to the UE 403, a number of stepsare required to be performed. Firstly, it is beneficial for theinitiating UE to have knowledge of the other D2D capable UEs withinrange. In an LTE system this may be achieved for example by each UEperiodically transmitting a discovery signal containing a unique“discovery” identifier that identifies UEs to one another.Alternatively, a serving eNodeB or coordinating entity may compile alist of UEs within its coverage area capable of performing D2Dcommunications and distribute the list to the appropriate UEs within itscoverage area. By virtue of either of the above processes the UE 401 maydiscover UE 402, UE 402 may discover UEs 401 and 403, and UE 403 maydiscover UE 402.

Previously Proposed D2D Systems

It has previously been proposed to provide some arrangement for deviceto device communication within standards which define communicationssystems according to specifications administered by the 3GPP referred toas Long Term Evolution (LTE). A number of possible approaches to theimplementation of LTE D2D communications exist. For example, thewireless access interface provided for communications between UEs andeNodeB may be used for D2D communications, where an eNodeB allocates therequired resources and control signalling is communicated via the eNodeBbut user data is transmitted directly between UEs.

The wireless access interface utilised for D2D communications may beprovided in accordance with any of a number of techniques, such ascarrier sense multiple access (CSMA), OFDM or a combination thereof forexample as well as an OFDM/SC-FDMA 3GPP LTE based wireless accessinterface. For example it has been proposed in document R2-133840 [1] touse a Carrier Sensed Multiple Access, CSMA, co-ordinations oftransmission by UEs, which is un-coordinated/contention based schedulingby each UE. Each UE first listens then transmits on an unused resource.

In another example, UEs may communicate with each other by negotiatingaccess to a wireless access interface directly, thus overcoming the needfor a coordinating eNodeB. Examples of previously proposed arrangementsinclude those in which one of the UEs of the group acts as a controllingentity to co-ordinate the transmissions of the other members of thegroup. Examples of such proposals are provided in the followingdisclosures:

-   -   R2-133990, Network control for Public Safety D2D Communications;        Orange, Huawei, HiSilicon, Telecom Italia    -   R2-134246, The Synchronizing Central Node for Out of Coverage        D2D Communication; General Dynamics Broadband UK    -   R2-134426, Medium Access for D2D communication; LG Electronics        Inc In another arrangement one of the UEs of the group first        sends a scheduling assignment, and then transmits data without a        central scheduling UE or controlling entity controlling the        transmissions. The following disclosures provide examples of        this de-centralised arrangement:

R2-134238, D2D Scheduling Procedure; Ericsson;

-   -   R2-134248, Possible mechanisms for resource selection in        connectionless D2D voice communication; General Dynamics        Broadband UK;    -   R2-134431, Simulation results for D2D voice services using        connectionless approach General Dynamics Broadband UK

In particular, the last two contributions listed above, R2-134248 [6],R2-134431 [7], disclose the use of a scheduling channel, used by UEs toindicate their intention to schedule data along with the resources thatwill be used. The other disclosure, R2-134238 [5], does not use ascheduling channel as such, but deploys at least some predefinedresources to send the scheduling assignments.

Other example arrangements disclosed in [8] and [9] require a basestation to provide feedback to the communications devices to controltheir transmissions. Document [10] discloses an arrangement in which adedicated resource exchanging channel is provided between cellular userequipment and device-to-device user equipment for interference controland resource coordination.

As a result of the possible approaches to the organisation of a D2Ddevices and networks, a number of scenarios may arise. A selection ofexample scenarios are provided by FIGS. 5a to 5d where each may causedifferent problems regarding the allocation of resources, the operationof D2D communications alongside conventional LTE communication and themovement of D2D capable devices between coverage areas provided byeNodeBs.

In FIG. 5a UEs 501 and 502 are outside of a coverage area of an eNodeB,consequently, the D2D devices may communicate with little or no regardfor interference that may be caused by their D2D communications toneighbouring LTE networks. Such a scenario may occur in public safetycommunications for example, where either the UEs are outside of acoverage area or where the relevant mobile communications network is notcurrently functioning correctly. In such a scenario the communicatingUEs may either negotiate directly with one another to allocate resourcesand coordinate communications, or one of the UEs or a third UE may actas a coordinating entity and therefore perform resource allocation.

In FIG. 5b UE 501 is within a coverage area 504 of an eNodeB 503 and isperforming D2D communications with UE 502 which is outside the coveragearea 503. In contrast to the scenario of FIG. 5a , by virtue of UE 501being within the coverage area of the eNodeB 503, D2D communications maycause interference to conventional LTE communications within thecoverage area. Consequently, D2D resource allocations and transmissionsmay have to be coordinated around those within the coverage area 504 soconventional LTE communications are unaffected by D2D transmissions.This may be achieved in a number of ways, for example the eNodeB maycoordinate the resource allocation for the D2D communications so thatD2D resources and conventional LTE resources do not overlap. Anyallocations may then be relayed to UE 502 by UE 501. Alternatively, UE 1or UE2 via UE1 may for example perform resource allocation and theninform the eNodeB of the resources being utilised for D2Dcommunications. The eNodeB will then reserve these resources for D2Dcommunications.

In FIG. 5c both UE 501 and 502 are within the coverage area of theeNodeB 503, consequently, coordination between the eNodeB and UEs willbe required if D2D communications are to be performed without causinginterference to conventional LTE communications within the coveragearea. Such coordination may be achieved in a similar way to thatdescribed with reference to FIG. 5b but in the case of FIG. 5c UE 502 isalso within the coverage area and therefore the relaying of resourceallocation signals by UE1 to the eNodeB from UE 2 may not be required.

In FIG. 5d a fourth more complex D2D scenario is illustrated, where UE501 and UE 502 are each within the coverage areas 504 505 of differenteNodeBs 503 and 504 respectively. As for the scenarios of FIGS. 5b and5c , coordination between the UEs performing D2D communications will berequired if interference between D2D communications and conventional LTEcommunications is to be avoided. However, the presence of two eNodeBrequires that resource allocations by the eNodeBs within the coverageareas 504 and 505 are required to be coordinated around the D2Dresources allocations.

FIGS. 5a to 5d illustrates just four of a large number of possible D2Dusage scenarios, where further scenarios may be formed from combinationsof those illustrated in FIGS. 5a to 5d . For example, two UEscommunicating as shown in FIG. 5a may move into the usage scenario ofFIG. 5d such that there are two groups of UEs performing D2Dcommunications in the coverage areas of two eNodeBs.

Once a D2D communications link is established resources of the wirelessaccess interface are required to be allocated to the D2D link. Asdescribed above it is likely that D2D communication will take place inspectrum allocated for LTE networks, consequently it has been previouslyproposed that when within a coverage area of an LTE network, D2Dtransmission are performed in the uplink spectrum and that SC-FDM isused . . . . Furthermore, as one of the motivating factors behind D2Dcommunication is the increase in capacity that may result, utilising thedownlink spectrum for D2D communications is not appropriate.

As previously described it would be desirable to provide an arrangementfor D2D communications which do not significantly adversely affectconventional LTE communications when within a coverage area of one ormore eNodeBs. To accomplish D2D communications in such situations,coordination is required between the UEs wishing the preform D2Dcommunications and the serving eNodeB or predetermined knowledge of D2Dresources are required, so that D2D and conventional LTE communicationsare not scheduled for a same set of resources. Furthermore, because D2Dcommunications may coexist with conventional communications within asystem, it is also desirable that D2D resource allocations andtransmission do not interfere and are transparent to other UEs so anyadverse effects on other UEs are reduced. However, generally a technicalproblem can be seen to provide an arrangement for performing D2Dresource allocation, which reduces resource usage for schedulinginformation, and frees up resources for D2D data traffic. Accordinglyscheduling assignment is desirable to the effect that the availablecommunications resources can be allocated to the communications devicesof the group.

Improved Device-to-Device Communications

Example embodiments of the present technique can provide an arrangementin which D2D communications can be performed between one or morecommunications devices which may form a group of communications devices.The group of communications devices may be arranged to perform D2Dcommunication without requiring a central entity to control thetransmission of signals from the communications devices to the othercommunications devices of the group. According to the present technique,a wireless access interface is provided which includes a schedulingregion or channel in which scheduling assignment messages may betransmitted in a plurality of sections of communications resources. Thusthe scheduling region may be referred to as a scheduling assignmentregion or channel. Each of the plurality of communications resource hasa corresponding section of resources of a shared communications channel.The transmission of a scheduling assignment message in one of thesections of the scheduling region can provide an indication to all ofthe other devices in a group that a communications device wishes totransmit signals representing data in a corresponding section of theshared communications resources.

As will be understood from the following examples, a scheduling regionor channel within a wireless access interface provides communicationsdevices with a facility to transmit scheduling assignment messages inorder to reserve corresponding sections of communications resources of ashared communications channel. A communications device can transmit datato other communications devices in a group by transmitting a schedulingassignment message in one or more of the plurality of predeterminedsections of the scheduling region. The transmission of the schedulingassignment message in a section of the scheduling region informs theother devices of the group that a communications device will transmitsignals representing data in at least one corresponding section of theshared communications channel. Other devices in the group which are nottransmitting therefore monitor the scheduling region and if they detecta scheduling assignment message transmitted in one or more sections ofthe schedule assignment region then attempt to detect and decode signalstransmitted in a corresponding section or sections of the sharedcommunications resources channel. Accordingly a group of communicationsdevice can perform D2D communications with improved resource efficiency.

In some examples, the schedule assignment region is providedperiodically in time divided units separated by one or more other timedivided units which provide the shared communications resources.Accordingly a power saving advantage is provided to communicationsdevices of the group because the devices power up their receivers toreceive the scheduling region periodically, the period corresponding tothe relative ratio of the time unit in which the scheduling region isprovided with respect to the time unit or units in which the sharedcommunications resources are provided.

An example application is presented in FIG. 6. In FIG. 6, a plurality ofcommunications devices 101 form a group of communications devices 604for which D2D communications is desired for the reasons explained above.As represented in FIG. 6, the communications devices 101 are outside acoverage area represented by a broken line 601 of a base station 602. Assuch the base station 602 cannot form or control any of thecommunications between the devices. However as mentioned above in someexamples the group of communications devices may operate within acoverage area provided by the base station 602 and accordingly it isdesirable that the transmission of signals by the communications devices101 does not interfere with transmissions to or from the e-Node B 602 byconventional communications devices. As such, in some examples, awireless access interface which is formed by the communications devices101 for performing the D2D communications may utilise an uplinkfrequency of a conventional communications device. The wireless accessinterface can be arranged to transmit signals to the eNode B 602 whenoperating in a conventional mode, and to transmit and receive data via amobile communications network of which the base station 602 forms apart.

As shown in FIG. 6, each of the UEs 101 includes a transmitter 606 and areceiver 608, which perform the transmission and reception of signalsunder the control of the controller 610. The controller 610 control thetransmitter 606 and the receiver 608 to transmit and receive databetween members of the group to perform D2D communications.

A wireless access interface which is configured to provide anarrangement for D2D communications is presented in FIG. 7. In FIG. 7,the wireless access interface is formed from a plurality of OFDM subcarriers 701 and a plurality of OFDM symbols 702 which can be dividedinto sections of communications resources. As shown in FIG. 7, thewireless access interface is divided into time divided units of subframes 704, 706, 708, 710 of communications resource. As shown in FIG.7, every other sub frame includes a scheduling region 712, 714. Thescheduling region includes a plurality of sections of communicationsresource which are numbered in FIG. 7 from 1 to 84. A remaining part ofthe sub frame 704, 708 in which a scheduling region 712, 714 is includedis divided into a plurality of sections of shared communicationsresources. Other sub frames in which there is no scheduling region 712,714 are divided into sections of shared communications resource for thetransmission of signals representing data by the communications deviceto other communications devices within the group. However, incombination a plurality of sections of communications resources ofshared resources are provided within two sub frames 704, 706, 708, 710and each of the sections of shared resource corresponds to one of thesections of the scheduling region 712, 714. Accordingly, in accordancewith the present technique, a transmission by a communications device inone of the sections of the scheduling region of a scheduling assignmentmessage indicates to the other communications devices within the groupthat the communications device which transmitted the schedulingassignment message in that section of the scheduling region intends totransmit data in a corresponding section of the shared communicationsresources in which data can be transmitted. Thus as represented by thearrow 720, the transmission of a scheduling assignment in section 81 ofthe scheduling region 712 provides an indication to the othercommunications devices in the group that the transmitting communicationsdevice that transmitted the scheduling assignment message intends totransmit data in the section numbered 81 of the scheduling assignmentresource.

FIG. 7 therefore shows a potential arrangement for implicit resourcescheduling. For the example shown in FIG. 7, the scheduling assignmentresource or region 712 has been chosen to be one uplink resource blockof a conventional LTE wireless access interface, transmitted everysecond subframe. However other configurations could be made as will beexplained below. For simplicity, each traffic resource has been splitinto four device-to-device resource blocks. In some examples resourceblocks for the device-to-device communications may not be the same as aconventional resource block for LTE. However as will be appreciated fromthe above explanation, each resource element of the schedulingassignment resource or region directly refers to a traffic resourceblock in the shared communications resources available to the D2Dcommunications devices two subframes later. Accordingly, anycommunications device in the group of communications devices 604 or ascheduling communications device/eNodeB can use this schedulingassignment channel to indicate where it will transmit data.

In some examples, the scheduling assignment message may include one ormore identifiers which may include but are not limited to an identifierof the transmitting communications device, an identifier of thedestination device or devices, a logical channel identifier, transportchannel identifier, and application identifier, or an identifier of thegroup of communications devices depending upon the application. Forexample if the group of communications devices were engaged in apush-to-talk communications session, then the scheduling assignmentmessage would not need to identify the individual device, but only thegroup of communications devices. Other devices within the group, whichdetect the transmission of the scheduling assignment message in asection of the scheduling region will know not to attempt to transmit inthe corresponding section of the shared communications resources fortransmitting data and will detect the identifier of the group ofcommunications devices.

The devices of the group will therefore know to listen and to receivethe data transmitted by the transmitting communications devices (UE),which transmitted the scheduling assignment message, which included thegroup identifier.

As shown in FIG. 7 the resource numbered 81 corresponds to a region inthe next available communications resource for that number that is inthe third sub frames 708. Thus there is a corresponding delay betweentransmission of the scheduling assignment message and the transmissionof the data in order to provide notice to the other communicationsdevices in the group that that particular section of the sharedcommunications resources has been reserved by one of the communicationsdevices for transmission.

The scheduling assignment message may in some examples include otherinformation, for example information which is required for security, orinformation which identifies the type of content which will be sent inthe shared resources such as discovery messages, or D2D voice or datatraffic.

In some examples the scheduling assignment message transmitted by acommunications device (UE), which intends to transmit data, may includean indication of a plurality of the sections of the sharedcommunications resources in which it intends to transmit data. Forexample, the scheduling assignment message may include parameters N andM to schedule a block of N×M communications resource blocks from theshared communications resource channel. In one example the N×M resourceblocks may indicated in the scheduling assignment message with respectto the section of the scheduling region in which the message wastransmitted. This can be achieved by pre-configuring the controllers inthe communications devices to recognise that a scheduling assignmentmessage providing the parameters N and M will identify that the N×Mcommunications resources blocks starting from the corresponding sectionin the shared communications resources channel to the section in thescheduling region in which the scheduling assignment message wastransmitted.

Other Configurations of D2D Wireless Access Interface

As will be appreciated the arrangement of the wireless access interfaceof FIG. 7 for D2D communications by the group of devices shown is oneexample. There may also be other defined/fixed patterns of resourcereservation that can be indicated with a resource element, which mayspan more than a just a few subframes and the scheduling assignmentresource might take more than just one resource block.

Another example is shown in FIG. 8 where corresponding sections ofwireless access interface and features have corresponding referencenumerals. In contrast to the arrangement showing in FIG. 7 the wirelessaccess interface shown in FIG. 8 includes only a single schedulingregion 712 and correspondingly the regions of shared resource for whichthere is a corresponding section of the scheduling region contain agreater amount of resources. In FIG. 8, examples are shown in whichdifferent communications devices reserve sections of resource of theshared communications resources channel by transmitting schedulingassignment messages in each of the sections of the scheduling region. Inthe above FIG. 8, the entire resource block is used for schedulingindividual D2D resource blocks for the next four subframes. For example,a first communications device transmits scheduling assignment messagesin sections 1, 9, 10, 11, 12, 16, 17, 18, 19 as shown by the darkestsections 801 whereas a second communications device transmits ascheduling assignment messages in the sections 23, 24, 25, 26, 30, 31,32, 33, 34, 35, 37, 38, 39, 40, 41, 42 reserving the correspondingsections 804 whereas a third communications device transmits schedulingassignment messages in sections 3, 4, 5, 6, 7, 13, 14, 20, 21, 27, 28reserving the lighter coloured sections 806 of the shared communicationschannel. Two resource blocks remain unused in this case, which couldcontain other control information. This is perhaps not a likely way tosplit resources but is included as an illustrative example.

A further example arrangement is shown in FIG. 9 of a wireless accessinterface which corresponds to another example arrangement of thepresent technique. As shown in FIG. 9, resources in the shared uplinktransmission channel are divided into sections 1 to 252 and thecorresponding scheduling region 901, 904 is divided into sections 1 to252. In FIG. 9 another potential arrangement is shown, which allows moreflexible scheduling. Each resource element in the scheduling channelcorresponds to one traffic resource block. This means that thesub-carrier containing the scheduling region, and hence headerinformation such as group identifier, will be the same sub-carrier wherethe traffic/payload part will be found. Although this is taking more ofthe available communications resources for scheduling information, itstill provides the benefit that a UE can monitor with the schedulingregion with discontinuous reception (DRX) and hence save power, ratherthan having to monitor all data blocks. It also uses communicationsresources more efficiently by not requiring header information to besent with every block of data, if the communications devices areconfigured to specify one resource element in the scheduling channelalong with a block of M×N resource blocks, in which they intend totransmit data. As with the above examples it would be preferable to usethe scheduling assignment messages to reserve several resource blocksrather than individual resource blocks, because this would be moreefficient.

FIG. 10 provides further examples of wireless access interfaces, whichare configured, in accordance with the present technique, to provide afacility for D2D communications. In a first example FIG. 10a , aconventional LTE uplink carrier provides a plurality of resource blockscomprising OFDM symbols and subcarriers. In the example illustration, aswith the examples shown in FIGS. 7, 8 and 9, one square represents atraditional resource block. Areas having different shading representcontrol (scheduling assignments) and traffic from different UEs. Theamount of traffic reserved by a scheduling assignment may be larger orsmaller than shown above. The scheduling assignment messages may alsohave a different size, depending on the amount of information which theyneed to convey. They may also be sent more or less frequently.

For the example showing in FIG. 10a a first section of the uplinkcommunications channel 1001 is assigned to conventional uplinkcommunications of an LTE uplink carrier. As explained above the top andbottom sections of resource 1002, 1004 are devoted to uplink controltransmissions according to a conventional LTE arrangement. However, asection of resources 1006 is devoted to provide a scheduling region fortransmitting scheduling assignment messages and control messages bydevices operating to perform D2D communications. A second region 1008 isassigned to shared communications resources for D2D communications whichare assigned by transmitting a scheduling assignment message in thecorresponding region of the scheduling region 1006. These above examplesare not limiting.

For the example illustrated in FIG. 10a , the frequency of thescheduling assignment messages implies the frequency of the data. Thereceiving UE detects a scheduling assignment message in the schedulingresources, and decodes the information which contains for example agroup identifier for which it is a member. The UE then continuesdecoding this frequency to obtain the traffic information.

FIG. 10b provides a similar configuration. However for the example shownin FIG. 10b the scheduling region 1010 has a shorter duration allowingthe region for data transmissions 1012 to be larger. According to thisexample the scheduling assignment from different UEs are sent atdifferent times. The timing implies the frequency of the datatransmissions. In contrast the example of FIG. 10c provides a largerscheduling region 1014 and a smaller shared resources region 1016.

In this example, the scheduling assignment messages are transmittedrepeatedly a number of times before sending data. This example may helpwith for example contention resolution.

For examples shown in FIGS. 10d and 10e a further differentconfiguration and partitioning of the scheduling region and the datatransmission region is made. In FIG. 10d a first scheduling region 1020is provided with a larger shared resource region 1022. For the exampleshown in FIG. 10e the scheduling region comprises a first region 1030and a second region 1032 and the resources in between 1034 are allocatedfor shared communications resources for data transmission. The examplesshown in FIGS. 10d and 10e illustrate examples of possible ways for thedata itself to be time-multiplexed rather than by frequency. The timingof the scheduling assignments imply the timing of the data.

Contention Resolution

The embodiments of the present technique described above provide anarrangement in which a communication device can transmit a schedulingassignment message in preparation for transmitting data in a section ofshared communications resources, which corresponds to the section of ascheduling region in which the scheduling assignment message wastransmitted. As will be appreciated there is a finite probability thatone of the other devices may contemporaneously transmit a schedulingassignment message in the same scheduling assignment section andsubsequently transmit signals representing the data being communicatedin the corresponding section of the shared resources. In some exampleembodiments a contention resolution arrangement may be used in order todetect the transmission of signals contemporaneously by two or morecommunications devices of the group so that each of the communicationsdevices of the group may retransmit their scheduling assignment messagein another scheduling assignment section at a later subframe. In otherexamples the communications devices may accept the loss of thetransmission of the data and high layer protocols may arrange for thisdata to be retransmitted. In other examples a collision avoidancemechanism may be deployed, in order to detect that a collision hasoccurred, so that a retransmission may be made. In some example one ormore of the communications devices of the group may transmit anindication that a collision has occurred, so that a re-transmission maybe performed. For example a push-to-talk application allows users todetect when more than one user has attempted to transmitcontemporaneously and the other users can request a re-transmission.

SUMMARY

According to the example embodiments explained above, a time andfrequency position of transmission of scheduling assignment messages inthe scheduling assignment channel/region determines, at least in part,the communications resources of a shared channel which will be used by aUE to transmit signals representing data, which is being transmitted toother communications devices. In some examples the scheduling assignmentmessages may include additional control/header information such asgroup/sender identification for security.

Embodiments of the present technique can therefore provide anarrangement in which D2D communications can be performed via a wirelessaccess interface in which a time-frequency position of a schedulingassignment message reduces the amount of information that needs to betransmitted and therefore consumes less radio resources for scheduling.Furthermore in some embodiments data and header parts of transmissionscan be separated, thereby using communications resources moreefficiently, and an identifier of the communications device or a groupof communications devices in which the communications device belongs maybe transmitted in the scheduling assignment message. As will beappreciated a further example is provided because a communicationsdevice only needs to monitor the scheduling assignment channel/regionwhich may occur relatively in frequently thereby allowing the device topower down so that it can save power. If the group of communicationsdevices are within range of an eNodeB, then the eNodeB can performscheduling, so that the communications device can be informed via theUp-link channel to all UEs in a group without having to establish aradio resource control (RRC) connection or scheduling via down-linkchannels.

Various further aspects and features of the present invention aredefined in the appended claims and various combinations of the featuresof the dependent claims may be made with those of the independent claimsother than the specific combinations recited for the claim dependency.Modifications may also be made to the embodiments hereinbefore describedwithout departing from the scope of the present invention. For instance,although a feature may appear to be described in connection withparticular embodiments, one skilled in the art would recognise thatvarious features of the described embodiments may be combined inaccordance with the disclosure.

In the foregoing description D2D communications are described withreference to an LTE system, however the presently disclosed techniquesare equally applicable to other LTE system structures and other systemswhich are compatible with D2D communications.

The following numbered clauses provide further example aspects andfeatures of the present technique:

1. A communications device comprising

a transmitter configured to transmit signals to one or more othercommunications devices via a wireless access interface to performdevice-to-device communications,

a receiver configured to receive signals from the one or more othercommunications devices via the wireless access interface, and

a controller for controlling the transmitter and the receiver totransmit or to receive the signals via the wireless access interface totransmit or to receive data represented by the signals, the wirelessaccess interface providing

a scheduling region comprising a plurality of predetermined sections ofcommunications resources, and

a plurality of predetermined sections of shared communicationsresources, wherein each of the plurality of predetermined sections ofthe scheduling region correspond to one of the plurality of sections ofthe shared communications resources, so that transmitting in one or moreof the plurality of the sections of the scheduling region reserves oneor more corresponding sections of the shared communications resourcesfor transmitting the signals representing the data.

2. A communications device according to clause 1, wherein the controlleris configured to control the transmitter

to transmit a message in one of the sections of the scheduling region,and

to transmit the signals representing the data in the section or sectionsof the plurality of shared communications resources which corresponds tothe section of the scheduling region in which the message wastransmitted.

3. A communications device according to clause 2, wherein the controlleris configured in combination with the receiver

to monitor signals transmitted within the plurality of the sections ofthe scheduling region, and

after detecting one or more messages transmitted in any of the pluralityof the sections of the scheduling region,

to detect signals transmitted in the sections of the sharedcommunications resources which correspond to the sections of the one ormore scheduling region in which the messages were received.

4. A communications device according to clause 1, 2 or 3, wherein thewireless access interface is divided into a plurality of time dividedunits and

the scheduling region comprising the plurality of the predeterminedsections of communications resources is provided in one of the timedivided units, and

the plurality of sections of the shared communications resources isprovided in at least one other of the time divided units.

5. A communications device according to clause 4, wherein

the scheduling region comprising the plurality of the predeterminedsections of communications resources is provided periodically in thetime divided units, the occurrences of the scheduling region beingseparated by one or more time divided units providing the plurality ofsections of the shared communications resources, the period of thescheduling regions being determined by the one or more time dividedunits of the shared communications resources between the time dividedunits of the scheduling regions.

6. A communications device according to any of clauses 1 to 5, whereinthe messages include an indication of more than one of the sections ofthe shared communications resources in which the signals representingthe data are to be transmitted, at least one of the more than onesections of the shared communications resources corresponding to thesection of the scheduling region in which the message was transmitted.

7. A communications device according to clause 6, wherein the messagesinclude parameters N and M, which represent N resource blocks in timeand M resource blocks in frequency of the blocks of the sharedcommunications resources.

8. A communications device according to clause 6 or 7, wherein themessages include an identifier of the communications device, whichtransmitted the scheduling assignment message.

9. A communications device according to clause 6 or 7, wherein the oneor more communications devices form a group, and the messages include anidentifier of the group of the one or more communications devices whichtransmitted the message.

10. A communications device according to clause 6 or 7, wherein themessages include information identifying the type of information whichwill be sent in the shared resources.

11. A communications device according to any of clauses 4 to 10, whereinthe one or more sections of the shared communications resources whichare reserved for the transmission of signals representing the data bytransmitting the message in the corresponding section of the schedulingregion are separated from the scheduling region in which the message wastransmitted by at least one time unit.

12. A communications device according to any of clauses 1 to 10, wherein

the transmitter is configured to transmit signals to an infrastructureequipment of a mobile communications network via the wireless accessinterface,

the receiver is configured to receive signals from the infrastructureequipment via the wireless access interface, and

the controller is configured to control the transmitter and the receiverto transmit or to receive the signals to or from the infrastructureequipment via the wireless access interface to transmit or to receivedata represented by the signals via the mobile communications network,the wireless access interface being formed by scheduling the signals forreception by the communications devices and the transmission of signalsfor transmission by the communications device providing

a downlink reception channel comprising a down-link control channel anda downlink shared communications resources for allocation to thecommunications device to receive the signals representing the data, and

an uplink transmission channel including an up-link control channel anduplink shared communications resources for allocation to thecommunications device to transmit the signals representing the data tothe infrastructure equipment, the allocation of the communicationsresources of the downlink shared channel and the communicationsresources of the uplink shared channel being made by the infrastructureequipment, wherein the controller is configured in combination with thetransmitter and the receiver, when in a device to device mode, tore-configure the wireless access interface for use in transmitting thedata to the one or more other communications devices, the re-configuredwireless access interface comprising, within the uplink transmissionchannel,

the scheduling region comprising the plurality of the predeterminedsections of communications resources within the up-link transmissionchannel, and

the plurality of sections of the shared communications resources areprovided within the up-link transmissions channel.

13. A method of communicating data comprising

transmitting signals to one or more other communications devices via awireless access interface to perform device-to-device communications,

receiving signals from the one of the other communications devices viathe wireless access interface, and

controlling the transmitter and the receiver to transmit or to receivethe signals via the wireless access interface to transmit or to receivedata represented by the signals, the wireless access interface providing

a scheduling region comprising a plurality of predetermined sections ofcommunications resources, and

a plurality of sections of shared communications resources, wherein eachof the plurality of predetermined sections of the scheduling regioncorrespond to one of the plurality of sections of the sharedcommunications resources, so that transmitting in one of the pluralityof the sections of the scheduling region reserves at least onecorresponding section of the shared communications resources fortransmitting the signals representing the data.

14. A method according to clause 13, comprising

transmitting a message in one of the sections of the scheduling region,and

transmitting the signals representing the data in the section orsections of the plurality of shared communications resources whichcorresponds to the section of the scheduling region in which the messagewas transmitted.

15. A method according to clause 13, comprising

monitoring signals transmitted within the plurality of the sections ofthe scheduling region, and

after detecting one or more messages transmitted in any of the pluralityof the sections of the scheduling region,

detecting signals transmitted in the sections of the sharedcommunications resources which correspond to the sections of the one ormore scheduling region in which the messages were received.

16. A method according to clause 13, 14 or 15, wherein the wirelessaccess interface is divided into a plurality of time divided units and

the scheduling region comprising the plurality of the predeterminedsections of communications resources is provided in one of the timedivided units, and

the plurality of sections of the shared communications resources isprovided in at least one other of the time divided units.

17. A method according to clause 15, wherein

the scheduling region comprising the plurality of the predeterminedsections of communications resources is provided periodically in thetime divided units, the occurrences of the scheduling region beingseparated by one or more time divided units providing the plurality ofsections of the shared communications resources, the period of thescheduling regions being determined by the one or more time dividedunits of the shared communications resources between the time dividedunits of the scheduling regions.

18. A method according to any of clauses 13 to 17, wherein the messagesinclude an indication of more than one of the sections of the sharedcommunications resources in which the signals representing the data areto be transmitted, at least one of the more than one sections of theshared communications resources corresponding to the section of thescheduling region in which the message was transmitted.

19. Circuitry for a communications device comprising

transmitter circuitry configured to transmit signals to one or moreother communications devices via a wireless access interface to performdevice-to-device communications,

receiver circuitry configured to receive signals from the one or moreother communications devices via the wireless access interface, and

controller circuitry for controlling the transmitter and the receiver totransmit or to receive the signals via the wireless access interface totransmit or to receive data represented by the signals, the wirelessaccess interface providing

a scheduling region comprising a plurality of predetermined sections ofcommunications resources, and

a plurality of predetermined sections of shared communicationsresources, wherein each of the plurality of predetermined sections ofthe scheduling region correspond to one of the plurality of sections ofthe shared communications resources, so that transmitting in one or moreof the plurality of the sections of the scheduling region reserves oneor more corresponding sections of the shared communications resourcesfor transmitting the signals representing the data.

20. Circuitry according to clause 19, wherein the controller circuitryis configured to control the transmitter circuitry

to transmit a message in one of the sections of the scheduling region,and

to transmit the signals representing the data in the section or sectionsof the plurality of shared communications resources which corresponds tothe section of the scheduling region in which the message wastransmitted.

21. Circuitry according to clause 19, wherein the controller circuitryis configured in combination with the receiver circuitry

to monitor signals transmitted within the plurality of the sections ofthe scheduling region, and

after detecting one or more messages transmitted in any of the pluralityof the sections of the scheduling region,

to detect signals transmitted in the sections of the sharedcommunications resources which correspond to the sections of the one ormore scheduling region in which the messages were received.

References

[1] R2-133840, “CSMA/CA based resource selection,” Samsung, published at3GPP TSG-RAN WG2 #84, San Francisco, USA, 11-15 Nov. 2013.

[2] R2-133990, “Network control for Public Safety D2D Communications”,Orange, Huawei, HiSilicon, Telecom Italia, published at 3GPP TSG-RAN WG2#84, San Francisco, USA, 11-15 Nov. 2013.

[3] R2-134246, “The Synchronizing Central Node for Out of Coverage D2DCommunication”, General Dynamics Broadband UK, published at 3GPP TSG-RANWG2 #84, San Francisco, USA, 11-15 Nov. 2013.

[4] R2-134426, “Medium Access for D2D communication”, LG ElectronicsInc, published at 3GPP TSG-RAN WG2 #84, San Francisco, USA, 11-15 Nov.2013.

[5] R2-134238, “ D2D Scheduling Procedure”, Ericsson, published at 3GPPTSG-RAN WG2 #84, San Francisco, USA, 11-15 Nov. 2013.

[5] R2-134248, “Possible mechanisms for resource selection inconnectionless D2D voice communication”, General Dynamics Broadband UK,published at 3GPP TSG-RAN WG2 #84, San Francisco, USA, 11-15 Nov. 2013.

[7] R2-134431, “Simulation results for D2D voice services usingconnectionless approach”, General Dynamics Broadband UK, published at3GPP TSG-RAN WG2 #84, San Francisco, USA, 11-15 Nov. 2013.

[8] “D2D Resource Allocation under the Control of BS”, Xiaogang R. etal, University of Electronic Science and Technology of China,https://mentor.ieee.org/802.16/dcn/13/16-13-0123-02-000n-d2d-resource-allocation-under-the-control-of-bs.docx

[9] US20130170387

[10] US20120300662

[11] LTE for UMTS: OFDMA and SC-FDMA Based Radio Access, Harris Holmaand Antti Toskala, Wiley 2009, ISBN 978-0-470-99401-6.

1. A communications device comprising a transmitter configured totransmit signals to one or more other communications devices via awireless access interface to perform device-to-device communications, areceiver configured to receive signals from the one or more othercommunications devices via the wireless access interface, and acontroller for controlling the transmitter and the receiver to transmitor to receive the signals via the wireless access interface to transmitor to receive data represented by the signals, the wireless accessinterface providing a scheduling region comprising a plurality ofpredetermined sections of communications resources, and a plurality ofpredetermined sections of shared communications resources, wherein eachof the plurality of predetermined sections of the scheduling regioncorrespond to one of the plurality of sections of the sharedcommunications resources, so that transmitting in one or more of theplurality of the sections of the scheduling region reserves one or morecorresponding sections of the shared communications resources fortransmitting the signals representing the data.
 2. A communicationsdevice as claimed in claim 1, wherein the controller is configured tocontrol the transmitter to transmit a message in one of the sections ofthe scheduling region, and to transmit the signals representing the datain the section or sections of the plurality of shared communicationsresources which corresponds to the section of the scheduling region inwhich the message was transmitted.
 3. A communications device as claimedin claim 2, wherein the controller is configured in combination with thereceiver to monitor signals transmitted within the plurality of thesections of the scheduling region, and after detecting one or moremessages transmitted in any of the plurality of the sections of thescheduling region, to detect signals transmitted in the sections of theshared communications resources which correspond to the sections of theone or more scheduling region in which the messages were received.
 4. Acommunications device as claimed in claim 1, wherein the wireless accessinterface is divided into a plurality of time divided units and thescheduling region comprising the plurality of the predetermined sectionsof communications resources is provided in one of the time dividedunits, and the plurality of sections of the shared communicationsresources is provided in at least one other of the time divided units.5. A communications device as claimed in claim 4, wherein the schedulingregion comprising the plurality of the predetermined sections ofcommunications resources is provided periodically in the time dividedunits, the occurrences of the scheduling region being separated by oneor more time divided units providing the plurality of sections of theshared communications resources, the period of the scheduling regionsbeing determined by the one or more time divided units of the sharedcommunications resources between the time divided units of thescheduling regions.
 6. A communications device as claimed in claim 1,wherein the messages include an indication of more than one of thesections of the shared communications resources in which the signalsrepresenting the data are to be transmitted, at least one of the morethan one sections of the shared communications resources correspondingto the section of the scheduling region in which the message wastransmitted.
 7. A communications device as claimed in claim 6, whereinthe messages include parameters N and M, which represent N resourceblocks in time and M resource blocks in frequency of the blocks of theshared communications resources.
 8. A communications device as claimedin claim 6, wherein the messages include an identifier of thecommunications device, which transmitted the scheduling assignmentmessage.
 9. A communications device as claimed in claim 6, wherein theone or more communications devices form a group, and the messagesinclude an identifier of the group of the one or more communicationsdevices which transmitted the message.
 10. A communications device asclaimed in claim 6, wherein the messages include information identifyingthe type of information which will be sent in the shared resources. 11.A communications device as claimed in claim 4, wherein the one or moresections of the shared communications resources which are reserved forthe transmission of signals representing the data by transmitting themessage in the corresponding section of the scheduling region areseparated from the scheduling region in which the message wastransmitted by at least one time unit.
 12. A communications device asclaimed in claim 1, wherein the transmitter is configured to transmitsignals to an infrastructure equipment of a mobile communicationsnetwork via the wireless access interface, the receiver is configured toreceive signals from the infrastructure equipment via the wirelessaccess interface, and the controller is configured to control thetransmitter and the receiver to transmit or to receive the signals to orfrom the infrastructure equipment via the wireless access interface totransmit or to receive data represented by the signals via the mobilecommunications network, the wireless access interface being formed byscheduling the signals for reception by the communications devices andthe transmission of signals for transmission by the communicationsdevice providing a downlink reception channel comprising a down-linkcontrol channel and a downlink shared communications resources forallocation to the communications device to receive the signalsrepresenting the data, and an uplink transmission channel including anup-link control channel and uplink shared communications resources forallocation to the communications device to transmit the signalsrepresenting the data to the infrastructure equipment, the allocation ofthe communications resources of the downlink shared channel and thecommunications resources of the uplink shared channel being made by theinfrastructure equipment, wherein the controller is configured incombination with the transmitter and the receiver, when in a device todevice mode, to re-configure the wireless access interface for use intransmitting the data to the one or more other communications devices,the re-configured wireless access interface comprising, within theuplink transmission channel, the scheduling region comprising theplurality of the predetermined sections of communications resourceswithin the up-link transmission channel, and the plurality of sectionsof the shared communications resources are provided within the up-linktransmissions channel.
 13. A method of communicating data comprisingtransmitting signals to one or more other communications devices via awireless access interface to perform device-to-device communications,receiving signals from the one of the other communications devices viathe wireless access interface, and controlling the transmitter and thereceiver to transmit or to receive the signals via the wireless accessinterface to transmit or to receive data represented by the signals, thewireless access interface providing a scheduling region comprising aplurality of predetermined sections of communications resources, and aplurality of sections of shared communications resources, wherein eachof the plurality of predetermined sections of the scheduling regioncorrespond to one of the plurality of sections of the sharedcommunications resources, so that transmitting in one of the pluralityof the sections of the scheduling region reserves at least onecorresponding section of the shared communications resources fortransmitting the signals representing the data.
 14. A method as claimedin claim 13, comprising transmitting a message in one of the sections ofthe scheduling region, and transmitting the signals representing thedata in the section or sections of the plurality of sharedcommunications resources which corresponds to the section of thescheduling region in which the message was transmitted.
 15. A method asclaimed in claim 13, comprising monitoring signals transmitted withinthe plurality of the sections of the scheduling region, and afterdetecting one or more messages transmitted in any of the plurality ofthe sections of the scheduling region, detecting signals transmitted inthe sections of the shared communications resources which correspond tothe sections of the one or more scheduling region in which the messageswere received.
 16. A method as claimed in claim 13, wherein the wirelessaccess interface is divided into a plurality of time divided units andthe scheduling region comprising the plurality of the predeterminedsections of communications resources is provided in one of the timedivided units, and the plurality of sections of the sharedcommunications resources is provided in at least one other of the timedivided units.
 17. A method as claimed in claim 15, wherein thescheduling region comprising the plurality of the predetermined sectionsof communications resources is provided periodically in the time dividedunits, the occurrences of the scheduling region being separated by oneor more time divided units providing the plurality of sections of theshared communications resources, the period of the scheduling regionsbeing determined by the one or more time divided units of the sharedcommunications resources between the time divided units of thescheduling regions.
 18. A method as claimed in claim 13, wherein themessages include an indication of more than one of the sections of theshared communications resources in which the signals representing thedata are to be transmitted, at least one of the more than one sectionsof the shared communications resources corresponding to the section ofthe scheduling region in which the message was transmitted. 19.Circuitry for a communications device comprising transmitter circuitryconfigured to transmit signals to one or more other communicationsdevices via a wireless access interface to perform device-to-devicecommunications, receiver circuitry configured to receive signals fromthe one or more other communications devices via the wireless accessinterface, and controller circuitry for controlling the transmitter andthe receiver to transmit or to receive the signals via the wirelessaccess interface to transmit or to receive data represented by thesignals, the wireless access interface providing a scheduling regioncomprising a plurality of predetermined sections of communicationsresources, and a plurality of predetermined sections of sharedcommunications resources, wherein each of the plurality of predeterminedsections of the scheduling region correspond to one of the plurality ofsections of the shared communications resources, so that transmitting inone or more of the plurality of the sections of the scheduling regionreserves one or more corresponding sections of the shared communicationsresources for transmitting the signals representing the data. 20.Circuitry as claimed in claim 19, wherein the controller circuitry isconfigured to control the transmitter circuitry to transmit a message inone of the sections of the scheduling region, and to transmit thesignals representing the data in the section or sections of theplurality of shared communications resources which corresponds to thesection of the scheduling region in which the message was transmitted.21. Circuitry as claimed in claim 19, wherein the controller circuitryis configured in combination with the receiver circuitry to monitorsignals transmitted within the plurality of the sections of thescheduling region, and after detecting one or more messages transmittedin any of the plurality of the sections of the scheduling region, todetect signals transmitted in the sections of the shared communicationsresources which correspond to the sections of the one or more schedulingregion in which the messages were received.